Characterisation of different one-stage blower configurations using 3D unsteady numerical flow simulations

This paper deals with the CFD investigation of the flow in a one-stage radial flow blower-aggregate. The main aim of this numerical study is to compute the relevant operating characteristics of the blower-aggregate and to determine detailed information about the flow characteristics inside it. The distributions of these flow characteristics in the blower determined by the commercial code ANSYS-FLUENT [1] are available to judge whether the elements of the blower are working properly, or not. The calculated characteristics of operating parameters are compared in this paper with measured data given by experimental tests of the blower-aggregate for their validation [2]. The blower-aggregates investigated numerically are noted by BA₁, BA₂ and BA₃ in this paper

The mixing time of the switch Markov chains: a unified approach

Since 1997 a considerable effort has been spent to study the mixing time of switch Markov chains on the realizations of graphic degree sequences of simple graphs. Several results were proved on rapidly mixing Markov chains on unconstrained, bipartite, and directed sequences, using different mechanisms. The aim of this paper is to unify these approaches. We will illustrate the strength of the unified method by showing that on any $P$-stable family of unconstrained/bipartite/directed degree sequences the switch Markov chain is rapidly mixing. This is a common generalization of every known result that shows the rapid mixing nature of the switch Markov chain on a region of degree sequences. Two applications of this general result will be presented. One is an almost uniform sampler for power-law degree sequences with exponent $\gamma>1+\sqrt{3}$. The other one shows that the switch Markov chain on the degree sequence of an Erd\H{o}s-R\'enyi random graph $G(n,p)$ is asymptotically almost surely rapidly mixing if $p$ is bounded away from 0 and 1 by at least $\frac{5\log n}{n-1}$.Comment: Clarification

Storability of some apricot varieties as affected by storage period

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Spatial and temporal variation of extremely abundant maxima of precipitation in Hungary during the period between 1951 and 2010

The study deals with the accumulated database of 16 meteorological stations in Hungary during a period of 60 years. The purposewas to reveal the spatial and temporal structure of the appearance of extreme values in the daily distribution of data concerning precipitation.We strived to answer the question whether the frequency of incidences of daily maxima did they change or not during the 60 year-long periodin the main growing regions of the country. It is demonstrated on geographical maps how the size and frequency of precipitation episodesensued, and what are the typical traits of changes in intensity as well as in frequency of happenings projected according to their spatial andtemporal distribution.From the point of view of fruit and vegetable growing, it is of prime interest what kind of frequency and intensity of changes occurredin precipitation. The temporal distribution of extremities though did not seem to change signifi cantly in some areas, but the recognitionof changes may help conspicuously the planning and the choice between alternatives of species and varieties as well as technologies ofhorticultural managements for the long run.Extremely intense rains during a short time may cause erosion and stagnant water, thus we have to know what are the odds of risk.The temporary distribution of changes helps us to judge upon the reality of anxieties, which are expected according to the existence of trends.Seasonal or monthly distribution is visualised by maps, what is expected and what is accidental as for a decision in planning. The spatialdistribution of coeffi cients of variation help us to decide what is the local chance of extreme happenings at different parts of the country andwhat is its coeffi cient of uncertainty. The risk of any undertaking dependent on conditions of weather could be expressed numerically by acoeffi cient of risk

Spatial and temporal variation of extremely abundant maxima of precipitation in Hungary during the period between 1951 and 2010

The study deals with the accumulated database of 16 meteorological stations in Hungary during a period of 60 years. The purpose was to reveal the spatial and temporal structure of the appearance of extreme values in the daily distribution of data concerning precipitation. We strived to answer the question whether the frequency of incidences of daily maxima did they change or not during the 60 year-long period in the main growing regions of the country. It is demonstrated on geographical maps how the size and frequency of precipitation episodes ensued, and what are the typical traits of changes in intensity as well as in frequency of happenings projected according to their spatial and temporal distribution. From the point of view of fruit and vegetable growing, it is of prime interest what kind of frequency and intensity of changes occurred in precipitation. The temporal distribution of extremities though did not seem to change signifi cantly in some areas, but the recognition of changes may help conspicuously the planning and the choice between alternatives of species and varieties as well as technologies of horticultural managements for the long run. Extremely intense rains during a short time may cause erosion and stagnant water, thus we have to know what are the odds of risk. The temporary distribution of changes helps us to judge upon the reality of anxieties, which are expected according to the existence of trends. Seasonal or monthly distribution is visualised by maps, what is expected and what is accidental as for a decision in planning. The spatial distribution of coeffi cients of variation help us to decide what is the local chance of extreme happenings at different parts of the country and what is its coeffi cient of uncertainty. The risk of any undertaking dependent on conditions of weather could be expressed numerically by a coeffi cient of risk

Relation of sour cherry blooming dynamics and meteorological variables

The aim of our research was to identify the role of weather parameters in the development of the start date and length of blooming.In order to achieve this, we examined how meteorological conditions of a particular year influence the start date and length of blooming indifferent years (dry, wet, cool, hot, sunny, cloudy). The meteorological parameters were the following: maximum temperature, minimumtemperature, average temperature, precipitation, length of sunlight, difference of daytime and nightime temperatures, potential evaporation-PET, Huglin-index,Winkler-index, climatic water balance which can be calculated as a difference of precipitation and potential evaporation.In this study we wanted to find out whether early start of blooming results in a longer blooming period or if there is a generally faster bloomingperiod when blooming starts later. Based on the results we can say that early start of blooming resulted in extended blooming period for threesour cherry varieties at the examined production sites. The start of blooming showed the closest relation with the difference of averagedaytime and nightime temperatures of the 30-day period prior to blooming. Significant relation was also detected with the thermic indexes aswell as with maximum temperatures, climatic water balance and the degree of potential evaporation.We examined how weather 30 days priorand during blooming influenced the length of phases. Results showed that precipitation prior and during blooming is in significant relationwith the length of blooming. We detected significant relation between daytime and nightime temperature differences and the length ofblooming. The nature of the relation indicates that blooming periods were shorter in case of increasing temperature differences.We found thatshorter blooming lengths occurred when maximum temperatures averaged between 13.5–14.5 ºC 30 days prior to blooming when examiningthe relation between blooming length and maximum temperature. If the average of maximum temperatures was below 13 ºC or exceeded15 ºC during this period, then we could calculate with a blooming period longer than ten days. We proved that little precipitation and hightemperature accelerates physiological processes, therefore we could calculate with an accelerated blooming and shorter blooming period

The effect of cooling irrigation on the blooming dynamic of plum

The objective of the present study is to explore the effect of cooling irrigation (aspersion) on the beginning of bloom and on the micro-climate of the plantation. The results show that the water sprayed in the orchard by micro-jet influenced decisively the temperature of the plantation. At higher temperatures (around 20 °C), the drop of temperature may attain 5–7 °C. A low relative humidity of the air may increase the relative effect, The frequent repetition (20 minute intervals) may keep the temperature low also in the buds. The beginning of bloom may delayed for more than ten days. The dynamics of blooming was characterised by a logistic curve in the treated as well as in the control plot. In the treated plot, the curve was steeper than in the control in spite of equal temperatures measured in the plots. Under our (Hungarian) climatic conditions, the method is successfully used to delay blooming dates. The main result is the diminution of the frost damage in the spring and the security of yield. The costs and water requirement should be calculated later

Damages caused by winter frosts, their temporal variation and frequencies in the main fruit growing region of Transdanubia and of the East Tisza regions of Hungary

The aim of the study was the study of winter frost damages, especially their changes expressed in temporal frequencies on the main fruit growing regions of the country. In our earlier paper, we introduced the calculation with the term LT50 as the quantitative expression of temperature threshold, when the lethality halves the survival of plant organs, buds or cells causing 50% death rate. The damage is highly dependent on the temperature and on its duration (length of time), but not at least on the frost tolerance of the fruit trees. The incidence and severity of damage is analysed according to the apricot and peach varieties of their different susceptibility or tolerance too. Four fruit growing regions, two of the in Transdanubia and two belonging to the regions east of the Tisza river have been selected to trace the incidence and severity of frost damages. For that purpose, we analysed the history of the past 60 year period, 1951–2010, utilising the database of the network of 16 meteorological stations of the countrywide service. Being aware of the values of LT50 during the rest period and afterward, the compulsory dormancy caused by low temperature, the number of days, the probability of frost damage could be predicted. The role of the orographical profi le, the height above sea level and the exposition of plantations are also decisive. Within the same plantation, 20–30 m difference of level may cause large diversity in temperature and frost damage. Air circulation and regular incidence of winds within the Carpathian basin modify the occurrence and severity of damages. Lowlands near the southern and northern country borders are particularly exposed to winter frosts. Most damages are reported in February, as temperatures below –20 °C especially if the fi rst part of the winter was mild, or in January was a warm period. With the end of the physiological rest period of the trees, the frost-susceptibility increases signifi cantly, and a cold period of –15 °C may cause heavy damage. This study proves that tolerance of varieties infl uence the damages substantially. By planting frost tolerant varieties, winter frost damages could be diminished by 40–50% at the same growing sites. Present results may also offer a tool to estimate the risk of frost damages and express the security of yields at a given site based on the data accumulated in the database over many years

Effect of over tree cooling irrigation on ‘Bosc’ pear orchards microclimate

Irrigation in some countries is a horticultural practice mainly used only to supply water. At the same time the use of microsprinklers have a powerful infl uence on the changes of temperature in orchards. When the air’s temperature is high (about 20 °C or higher) the evaporative cooling irrigation signifi cantly decreases the plants’ surface temperature and air temperature. The cooling effect is stronger when the air is dryer. By using cooling irrigation regularly, canopy temperature can be decreased so that the beginning of blooming can be delayed. Also if the blooming is early and frost probability is high, serious damages can happen in orchards. The benefi cial effect of cooling irrigation is the temperature reduction and frost protection. In March 2010, one month earlier than the expected blooming an irrigation system was established to produce anti-frost treatment and regulate the micro-climate of a Bosc pear orchard which belongs to the University of Debrecen (Hungary). The objective of sprinklers was to cool the air by increasing water evaporation and relative humidity. The position of the micro-sprinklers was planned in three levels (around the tree trunks, a few cm near to the soil surface, in the crown region and above the crown, a half meter higher). The results showed that the water sprayed in the orchard by micro-jets infl uenced decisively the temperature of the plantation. At higher temperatures (around 20 °C), the drop of temperature may attain 5–7 °C. A low relative humidity of the air may increase the relative effect. When water was applied at intervals of 15 minutes for ten times a day from 8 am to 18 pm, the air, fl owers and bud’s surface temperature could be kept low. At certain days when the temperature was higher than 10 °C, irrigation was used at night time in similar 15 minutes intervals, from 18 pm and 6 am. The beginning of bloom could be delayed for more than ten days. The Bosc pear variety blooming dynamics was characterized by a logistic curve in the treated as well as in the control plot. In the treated plot, the curve was steeper than in the control one in spite of the equal temperatures measured in the plots. Under Hungarian climatic conditions, the method was successfully used to delay blooming dates. The main result was the diminution of the frost damage in the spring that assured pears yields

Effect of over tree cooling irrigation on ‘Bosc’ pear orchards microclimate

Irrigation in some countries is a horticultural practice mainly used only to supply water. At the same time the use of microsprinklershave a powerful infl uence on the changes of temperature in orchards. When the air’s temperature is high (about 20 °C or higher)the evaporative cooling irrigation signifi cantly decreases the plants’ surface temperature and air temperature. The cooling effect is strongerwhen the air is dryer. By using cooling irrigation regularly, canopy temperature can be decreased so that the beginning of blooming can bedelayed. Also if the blooming is early and frost probability is high, serious damages can happen in orchards. The benefi cial effect of coolingirrigation is the temperature reduction and frost protection. In March 2010, one month earlier than the expected blooming an irrigation systemwas established to produce anti-frost treatment and regulate the micro-climate of a Bosc pear orchard which belongs to the University ofDebrecen (Hungary). The objective of sprinklers was to cool the air by increasing water evaporation and relative humidity. The position ofthe micro-sprinklers was planned in three levels (around the tree trunks, a few cm near to the soil surface, in the crown region and above thecrown, a half meter higher). The results showed that the water sprayed in the orchard by micro-jets infl uenced decisively the temperatureof the plantation. At higher temperatures (around 20 °C), the drop of temperature may attain 5–7 °C. A low relative humidity of the air mayincrease the relative effect. When water was applied at intervals of 15 minutes for ten times a day from 8 am to 18 pm, the air, fl owers andbud’s surface temperature could be kept low. At certain days when the temperature was higher than 10 °C, irrigation was used at night timein similar 15 minutes intervals, from 18 pm and 6 am. The beginning of bloom could be delayed for more than ten days. The Bosc pearvariety blooming dynamics was characterized by a logistic curve in the treated as well as in the control plot. In the treated plot, the curve wassteeper than in the control one in spite of the equal temperatures measured in the plots. Under Hungarian climatic conditions, the method wassuccessfully used to delay blooming dates. The main result was the diminution of the frost damage in the spring that assured pears yields